Radio compass navigation apparatus



Oct. 7, 1941. F. MOSELEY RADIO COMPASS NAVIGATION APPARATUS 4 Sheets-Sheet 1 Filed on. 22, 1937 fgnlm QEQ\S QE Q cs3 v Oct. 7, 1941. F. MOSELEY RADIO COMPASS NAVIGATION APPARATUS 4 Sheets-Sheet 2 Filed Oct. 22, 1937 I i I I I l I I l I l I I I l I I I 1 I I I I 'INVE'NTOR IIIIIIIIIIIIIIII IIIIIIIIIIIII'IIIIl-l'll'l' Patented Oct. 7, 1941 I I 2.251.551 RADIO COMPASS NAVIGATION APPARATUS Francis L. Moseley, Yonkers, N. Y., assignor to Sperry Gyroscope Company, Inc., N. Y., a corporation or New York B klyn.

Application October 22, 1937, Serial No. 170,308

I I 16 Claims. This invention relates, generally, to bearing or location inchcating navigation apparatus. and the invention has reference, more particularly. to a novel continuously operable, automatic orienting, radio compass navigation and control apparatus for use in the navigation of air, sea or land craft.

Heretofore, radio compasses have been used to some extent as aids to navigation. The early compasses employed loop antennae because of their marked directional signal characteristics. If such a loop is mounted in a vertical plane for rotation about a vertical axis, it produces a maximum signal pick-up output when the plane of the loop extends in the direction of the transmitting station, the pick-up output being a minimum or null when the plane of the loop is at with the incomable means for directly indicating either magnetic or true bearings of the craft or of the transmitting station or stations.

Still another object of the present invention is to provide novel radio compass navigation apparatus adapted for enabling the pilot to manually steer a homing course, while correcting for side gation apparatus employing directional signals ploy a non-directional antenna in coniunction Y with the loop antenna, the signal output of the non-directional antenna being combined with the loop signal by use of special switching and amplifying circuits so that a zero-center or rightleft meter may be operated therefrom. By use of such a meter the position of a station or stations can be ascertained and in navigation the radio compass became valuable since a direct "homing" course could be steered to the transmitting station, the pilot correcting the ship's care on the part of the operator in use, and in addition much time was consumed when it was desired to take bearings on a number of stations, as for determining position, andfurthermore these compasses generally were of uncertain utility owing to the 180 degree ambiguityflobtaining with most or them.

The principal object of the present invention is to provide navigation apparatus employing a novel automatic orientating radio compass giving continuous bearings throughout 360, a continuously operating servo system being provided to drive the radio loop so as to maintain the same automatically in the null position with respect to the incoming signal, 180 degree ambiguity being eliminated in the compass of this invention.

Another object of the present invention lies in the provision of a novel navigation apparatus employing a radio compass having easily operfor controlling the base line of the azimuth gyro oi an automatic -pilot, whereby the craft is steered automatically to a desired destination.

Still another object of the present invention is I to provide novel radio compass navigation apright angles to the direction of the station, 1. e.,

paratus of the above character having means for rotating a loop to a position of maximum signal for aural reception, with the non-directional antenna disconnected, in which position the receiver input is shielded from electrostatic induction and receives only electromagnetic waves.

Other objects and advantages will become ap parent from the specification, taken in connection with the accompanying drawings wherein the invention is embodied in concrete form.

In the drawings:

Fig. 1 is a schematic view of the novel automatic orientating radio compass navigation apparatus of this invention.

Fig. 2 is a wiring diagram of Fig. 1. I

Fig. 3 is a wiring diagram of a somewhat modifled arrangement.

Fig. 4 is a wiring diagram of an additional somewhat modified arrangement.

Similar-characters of reference are used in all of the above figures to indicate corresponding parts.

Referring now to Fig. 1 of the drawings, the reference numeral l designates a streamlined housing containing an electrostatically shielded loop 2 that is adapted to be rotated within housing i by a motor 3. Loop 2 is connected through leads I and i of cable I to a radio receiver and power supply unit 8 for feeding a directional signal voltage to this receiver. A non-directional antenna 9 is connected through lead II- for also supplyinga non-directional signal voltage to receiver I. 8 operates in a conventional manner, as will further appear, to produce right orleit voltage signals as loop 2 is turned to the right or left with respect to an incoming radio si nal wave front.

These right-left or directional signals are fed the apparatus of through cable l3 to a control panel ll having a radio compass pointer ll movable over a compass scale II. A selector switch knob I2 is mounted on panel II and may be turned to connect these right-left or directional signals to any of several devices which are operated therefrom. When the compass is to be operated in automatic orientation, switch knob I2 is turned to the position marked compass, thereby connecting the directional signals to motor control circuits contained in receiver 3, which circuits by operating either electric, electro-pneumatic or electronic relays,

serve to control the reversible loop drive motor 3. The motor 3 is thus caused todrive the loop 2 into alignment with the incoming signal wave front, while simultaneously turning compass pointer it through the flexible shaft connection l1, whereby pointer It moves over stationary scale I! to thereby indicate the bearing of the transmitting station with respect to some flxed line at the receiving station, for example the fore and aft axis of the craft carrying the receiving equipment. Thus, the fore and aft axis or reference line of the craft, such as an airplane, may extend through or parallel to the zero and 180 points of scale l5. As the heading of the craft starts to change, causing the loop to turn with respect to the incoming signal wave front, the

automatic servo mechanism is brought into play for operating motor 3 to turn the loop 2 to maintain the plane of the same at right angles to the signal direction and to cause pointer ll to continuously indicate the bearing of the station with respect to the craft s fore and aft axis. Thus, the pilot or navigator oi the craft has continuously available the station bearing without attention on his part other than initially tuning in the station by use of tuning knob l3 connected for selectively turning the tuning scales I3, 23 and 2|, corresponding to the three wave bands commonly used, especially on aircraft,

Positioned concentric with respect to flxed compass scale l5 and inwardly thereof is a rostable compass scale 23 that is connected to be turned by a set course" knob 22. The scale 23 is adapted to be turned so that the same reeats the reading of the crafts compass or direci nal g roscope as described in Patent No.

' 1.7 5270. Scale 23 is used when it is desired to nbta'n the magnetic bearing of the transmitting tation or the magnetic bearing of the craft from the station. .1. e., reversed bearings. To accomplish the manual setting of this scale, the pilot or navi ator first observes his compass course, as y vseni' the craft's compass or directional "W'ns 'rP-e so. He then turns the knob 22 until th s course indicated on scale 23 is opposite the ilxe' z'ero mark of the variation scale 23, whereupon the magnetic bearing of the station is indiated b the readin of pointer I on scale 23. A so. he reverse bearing. or the magnetic bearice of thecraft from the station is indicated directly by the reading of they tail portion ll of po nter II on scale 23. Thus, with pointer ll positioned as shown ,in Fig. l of the drawings, the position of the transmitting station with respect to the crafts heading or fore and aft axis is 45". Also. assuming scale 23 has been set to correspond to the ship's compass course, then this course is indicated as 0 or magnetic north, in which case the bearing of the station from the craft is 45 magnetic and the bearing of the craft from the station is read as 225 magnetic under the tail portion ll of pointer 13.. If it is desired to convert these readings to bearings relative to the true north, it is merely to turn knob 22 so that the crafts magnetic course indication on scale 23 is turned from the zero position of variation scale 24 to the point thereof corresponding to the compass variation of the locality in which the craft is located. Thus, assuming that the variation is 10f east, theninrig. lthe zero ofscale 23 ismovedsoas to be aligned with the 10 east point of variation scale 24, whereupon true bearings are indicated by pointer is on scale 23. In the example given in Fig. 1, these true bearings willbe 55 for the bearing of the station from the craft or 235 for the bearing of the craft from the station, this latter true bearing being suitable for application direct to a chart as in plotting position.

If it is desired to manually fly a homing course to a transmitting station, the selector switch knob I2 is turned to the homing" position and the pointersetting switch knob 2 is turned right or left, as the case may be, thus controlling drive motor 3 so that the'motor turns loop 2 and pointer ll to bring this pointer to zero position on scale I, whereby the plane of the loop extends at right angles to the fore and aft axis of the craft. The connections are now such that the directional signals from the receiver 3 are fed to a right-left indicator meter 21. By observing this meter and piloting the craft accordingly, a homing course can be flown to the transmitting station tuned in on one of the scales ll. 2|, 2|. The volume control knob is designated 33 andisonpanelll.

Should there be a side wind and the pilot desire to fly a straight course to the station, he can fly a "crabbing" or angle course to offset the eilect of the cross or side wind by operating switch 28 to turn loop l on to one side or the other, thereby setting in the desired wind correction. In setting the loop direction, the pilot selects the heading or loop angle which results in a directional gyroscope course that is constant.

If it is desiredto automatically fly a homing course to a transmitting station, the selector switch knob I2 is set in position marked Gyro pilot," in which position, with pointer II in zero position on scale IS, the directional signals from receiver I are fed through leads in a cable It to an electro-pneumatic valve 23 that is connected for controlling the base line of the azimuth or directional gyroscope 33 of the automatic pilot 3|. By turningpointer II from. zero position, correction for side wind can be made as in manually flying a homing course.

In the copending application of Bert G. Carlson, Serial No. 32,193, flied July 19, 1935, there is disclosed means for controlling the operation of an automatic or gyro pilot from a right-left radio compass, the novel compass of this invention beingadapted for performing the functions of the radio right-left indicator of that application.

Selector switch knob I2 may also be positioned on the shielded loop indication, in which positicn the pointer setting switch knob 28 may be turned to control motor 3 so as to cause loop'2 to be rotated to the podtion of maximum signal while the non-directional antenna 9 is disconnected. While in this position. the input to receiver I is shielded from electrostatic induction so that only electromagnetic waves aflect the receiver, thereby eliminating most of the undesired eflects of rains, sleet and snow, as is known to those skilled in the art.

Referring now to Fig. 2, wherein a wiring diagram of the structure of Fig. l, is given, the loop 2-for receiving the directional signals is shown as a divided or center tapped loop with its center tap grounded at 2'. Loop 2 is tuned by a condenser 32 connected across leads 5, I and operated from the tuning knob II. The output of loop 2 is fed through leads 5, i and blades 24, 35 of relay 38 through the double rectifier tube 31 and through resistor .41 to ground Oil. From tube 81 the directional R. F. signal voltage is applied through lead a, relay blade 29 and lead II to the control grid of an amplifier tube 4| along with the non-directional R. F. signal from antenna I, this latter signal through llandbladelltoleadlt' oscillator tube circuit 03 is energized from supply leads II, II through connecting II, II and supplies a low frequency altertlng current. of large amplitude compared to radio signals received on the loop, through transformer II and similar windings i5, 46

through R. I". chokes ll, 40' to the plates of double rectifier tube 31. I This low frequency A. Qacts aanalternatingbiassoasto cause the signal from the divided loop 2 to be alternately reversed in phase while being added to the output of the non-directional antenna 8, .whereby the voltage drop across the resistor 41 in the common plate-cathode circuit of tube 31 is caused to contain three principal components when the loop 2 is in position to receive energy from a transmitting station.

These three components are, firstly, a R. F. voltage supplied from loop 2 through tube 11 proportional to the strength of the received signal andto'theangularpositionofloop 2 inthe 8.1". field; secondly, a voltage supplied from non-directional antenna 9 proportional to the received signal,rand thirdly, a low frequency alternating voltage from oscillator 43 dependent in magnitude on the R. F. unbalance at the plates" of tube 21. Rectifier 31 thus serves as an electronlc switch and as a balanced modulator, so that a modulated R. F. signal is fed to the grid of tube ll whenever loop 2 is turned in the R. F. field to a receiving position.

The sign of the modulation is reversed, i. e., the peak of the modulation envelope is shifted 180' as divided loop 2 is turned to right or left from its null position with respect to the incoming signal by virtue of the addition of the nondirectional R. F. voltage in the rectifier plate circuit across resistor l1. The modulation envelope is fed through the untuned R. F. amplifier stage ll to the amplifier and detector 48 of any I coils II, I are fed with A. C. from oscillator through transformer 44. lead is and leads so and II. This circuit functions as a selective devicetooperateoneortheotheroftherelays II or II, depending upon the direction in'which theloop2isturnedwithrespecttoitsnullposiiion,i.e.,uponthephaseoftheaudiocutputoi' transformer".

'ihecontactsodrelayslhllareincircuitwith the armature oi the radio loop operating D. 0. motor). The field winding 65 of motor 3 is permanently connected across leads I and 62. 0peration of one of the relays I! or 58 connects the armature of motor I in one direction across the D. C. supply leads CI, 82, whereas operation of the other of these relays reverses the connection of this armature across leads ll, 2, hence reversing-the direction of operation of the motor 3. Thus, with coil 51' .of relay 51 energized, current from lead ii passes through current limiting resistance 3, the outer and center contacts of relay '1, lead 84 downwardly through the armature of motor I, and the center and inner contacts of relay 58 to lead 62; whereas with coil 58' of relay 5. energized, current from lead ll passes through resistance 63, the outer and center contacts of relay 58, lead 64 up through the armature of motor I, and the center and inner contacts of relay II to lead 62. Thus, motor 3 serves to turn loop 2 to maintain the same in its null position with respect to the received signal and also simultaneously positions the pointer It with respect to compass scale It. Condensers 66 and i",-connected in shunt with coils I1 and I8, serve to filter the rectified A. C. in the relay coils to give approximately equivalent D. C. operation. Inasmuch as the plates of tubes 51, 58' are energized from the same low frequency source as that supplying the modulating frequency to double rectifier ll, namely oscillator 43, these tubes will detect any reversal in phase of the audio signal output of amplifier-detector 48 due to shift of loop-2 from null position thereby serving to drive motor I in the proper and shortest direction to cause indicator it to always correctly indicate the bearing of the transmitting stat-ion. The system is thus free of ambiguity present in systems requiring mental interpretation of a right-left or other indicator, the reading of which is the same for 0 and 180 bearings.

In order to prevent overrunning and hunting of motor I, the back E. M. F. across the armature of this motor, which is dependent among other things upon the motor speed, is conveyed through lead N and resistors 60 and 68' to the grid bias circuit of tubes 53 and 53' through dividing resistors 69, 89'. Thus, the voltage cross the armature of motor 3 acts on tubes 53, 52' in a direction to cut the plate current of the driving tube 53 or 53', as the case may be, to zero before the loop is fully restored to null position, whereby motor I is brought to rest in a dead beat manner and without overshooting. This method of preventing hunting is disclosed in my copending application joint with Eric J. Isbister, Serial No. 83,844, filed June 6, 1936.

In operation, any ent .of the loop 2 with respect to the incoming signal direction causes a modulated R. F. signal to be fed from rectifier-modulator TI to the grid of amplifier tube ll, the sign of such modulation depending upon whether the loop is .turned to the right or left of its null position. The amplified lowfrequency modulated R. F. envelope enters the amplifier-detector I, from which it issues as low frequency to select either relay 51 or 58 and cause motor 2 to run and drive loop 2 to its null position, thus cutting off the input modtube 53 or 58', and'increase the plate current in the non-operating tube, servesto return the relays to normal position before the system reaches a balance, thereby avoiding overshooting and hunting.

When selector switch knob I2 is turned to the "horning or "B" position in order to manually fiy a homing course to a transmitting station, the selector switch arms I! and it" are connected to the respective terminals of the right-left or zero center meter 21, the supply for the plates of tubes 53 and 53' being from transformer ,lead ll and lead I. through resistors II and Ii. A condenser 12 is connected across the terminals of meter '21 to steady the pointer thereof. The pointer setting switch knob 28 serves to operate motor 3 so as to turn loop 2 and bring pointer II to zero (or fore and aft) position on scale It. Thus, when knob 28 is turned clockwise, its blade I! completes a circuit from lead 6|, lead ll, blade I3, lead 18, auxiliary relay coil I6 and lead II to negative lead 02. Coil 16' serves to operate the contacts of relay 58 and cause motor I to run in one direction,v

whereas when knob 25 is turned counter-clockwise, the auxiliary relay coil I! is similarly energized to operate relay 51 and turn motor I in the reverse direction. With pointer II on zero, the right-left indications of .meter 21 enable the pilot to fiy a homing course to the station,'and by correcting for side wind, as heretofore explained, he can fly a straight course to the station.

when the selector switch knob I2 is turned to "gyro pilot" or "C" position, the switch arms l2, I!" connect the plates of tubes II, II to the outer ends of solenoids 11, ll of electropneumatic valve 29 by leads II, II, a common return lead I! being connected to lead it. Solenoids I1, 11' serve to operate an armature II and hence a connected "balanced piston valve ii in opposite directions, depending on the direction in which the loop 2 is turned from its null position with respect to the incoming wave, whereby this valve controls the flow of air from inlet pipe 82 to pipes 83, ll leading to oppositely acting turbine wheels ll fixed on shaft 08.

Shaft l! is connected through reduction gearing 86 and differential gearing '1 to turn the air port carrying member ll of the automatic pilot directional gyro with respect to the cut-oil! plate I! in the manner disclosed in the previously mentioned Carlson application #32 ,193. This shifting of the base line of the directional gyroscope causes the same to eirect operation of the rudder servo motor (see Fig. l) to thereby actuate rudder ii to automatically fiy or steer the craft to the transmitting station, the pointer it having been set. by means 0! knob 28 on zero position of scale II. A follow back connection from the servo motor or rudder to-the air port carrying member II is provided by cable 02 around drum .3 operating the arm of diiferential gearing 81.

When the selector switch knob I2 is turned to the "shielded loop" or "D" position, the plates of tubes 83, ll are connected in parallel and the standby current through these tubes serves to actuate the relay ll. Current for this relay is supplied from oscillator. ll through transformer ll, lead ll, lead M, the operating coil of relay 3., lead II and switch arms I231!" to the plates of tubes I, It. The operation of relay it throws blades 42, SI, 34 and 38 to their upper contacts, in which position rectifier-modulator I1 and non-directional antenna I are disconnected from lead I. while the loop 21: connected through blades ll, CI, transformer ll, blade J0 and lead ll and amplifier II to the amplifier and detector 48 having the listening earphones 01 connected to the output thereof. Now by adjusting loop and pointer setting knob 2, the operator can turn the shielded loop 2 to the pomtion of maximum received signal as indicated by the earphones N, in which position, the undesired eifects of static produced by rains, sleet and snow. etc. are greatly reduced due to the elimination of electrostatic signals, thereby greatly facilitating ordinary aural reception.

The arrangement of Fig. 3 is similar to that of Fig.v 2 with the exception that a somewhat different form oi motor control'circuit is illustrated. In this figure the loop 2 and non-directional antenna I are connected to the loop switching circuits ll similar to that shown in Fig. 2, the amplifier and detector 08 being supplied irom such circuits, the low frequency modulation output of the amplifier and detector being fed to a transformer I00 similar to transformer 82 of Fig. 2. Transformer lllt supplies this low frequency modulation in pushpull or out of phase relation to the grids of a double triode l ll acting as amplifier and phase detector in that it detects the phase of the loop output, i. e. whether the loop is being turned to the right or left of its null position.

Theoutput of tube Ill is connected through condensers I, III to the grids of a double grid controlled rectifier tube IIII, so that the low frequency modulation corresponding in magnitude and phase to'the angular displacement and direction of turning of the loop I, is supplied to one of the grids of tube III, thereby causing this tube to be operated by graduated phase shift control as is known to those skilled in the art and as explained in articles by Albert W. Hull in the General Electric Review,;Vol. 32, Nos. 4 and 7, April and July, 1929. Tube III also serves as a rectifier in that it draws current from supply transformer I" through the impedance consisting of choke coil Ill and resistors Ill, lit, the current dividing at the mid tap of choke I" to fiow partly .up'through resistor I and the remainder down through resistor IN. The flow of this current produces an unbalanced D. C. component in choke III and in resistors I, IN in the manner described in detail in my copending application Serial No. 11,434 Joint with William T. Cooke, filed March 16, 1935, whereby as this D. CLcomponent varies, a voltage is induced across choke III, which voltage is in phase with the time rate of change of loop displacement, i. e., velocity, the first derivative of displacement with respect to time.

Thus, if an angular displacement of the loop occurs with respect to its null position, two D. C. voltages appear at the outer ends of resistors I, III, one proportional to and in phase with the angular displacement of the loop and the other proportional to and in phase with the velocity thereof. The combination of these voltages is applied to condensers III, III, and if these voltages are changing. the derivatives thereof with-respect to time are passed onto the grids-of tube; III in 180' out of phase relation, 1. e., D. C. surge voltages corresponding to the first and second derivatives of loop displacement with respect to time are supplied ..-to tube ill. The plates oftube I are suppliedfromtransformer I through bindings of Ill and III of induction motor 3' corresponding 5 to motor 3 of Figs. 1 and 2.

Theinner ends of said remaining windings of transformers Ill and IOI and the-inner ends of field windings I, II! are connected to opposite ends of a secondary of supply transformer I04.

When the upper plate circuit of tube I" is rendered conducting. the field winding I09 is enarmed to drive motor 3' in one direction, and

when the lower plate circuit of tube I" is rendered conducting, the field winding II! is is energized to drive the motor 3' in the opposite direction, thereby turning loop 2 and pointer I I, as desired. Inasmuch as rates are employed in controlling motor 2', the loop 2 is maintained in its null position at all times with substango tially no lag or hunting.

The arrangement of Fig. 3 is also adapted to be used for "homing," "gyro pilot" or shielded loop" control just as in the case of Fig. 2, the

selector switch l2 being adapted to be inserted 5 in the plate circuits of tube in just as in the case of tubes 52, ii of Fig.2.

In the form of the invention shown in Fig. 4, another somewhat different form of motor control circuit is illustrated. In this figure, the loop 2 and non-directional antenna 9 are connected to the loop switching circuits III similar to that shown in Fig. 2, the amplifier and detector III being supplied from such circuits, the variable magnitude, reversible phase audio signal output of the amplifier-detector III being fed to a transformer II2. This signal is amplified by tube Ill and passed through transformer III to push-pull stage III, where it is further amplified to a value sufficient for operation of one field winding III of a two-phase motor I" driving loop 2. This motor is thus driven in one direction or the other as the audio signal at transformer H2 is reversed by a change in the,

turned by spring action so that terminals F, l? are connected to winding Ili. Similarly. when switch III is moved so that contacts (3, G are connected to winding Hi, the motor 3" runs in the reverse or counter-clockwise direction.

Switch I24 serves for connecting the left-right or zero center meter 21 to the system, whereby the device may be used as a homing compass.

The power supply for the entire system of Fig. 4 is shown as furnished by the double-current generator I25. This generator is driven by a motor I21 which may be operated from any suitable power source as leads I2l. The output of the generator is shown consisting of a high voltage D. c. supplied to leads in for furnishing the plate voltage supply to'the various radio and amplifier stages, and a low frequency A. C. voltage supplied to leads I29 for use in controlling the loop switching circuits and the followup motor 3".

A switch I3. is provided in conjunction with switch I24 for feeding the reversing A. C. output of amplifier stage Hi to the reversing field winding III of a valve motor I32. Motor I22 is connected for turning the cut-off disc or plate III controlling the admission of air to ports I24, I34 leading through pipes 5,. I25 to the oppositely acting turbine wheels I28, I28, similar' to turbine wheels 84 of Fig. 2. As in Fig. 2, turbine wheels I38, I38 form a part of the automatic pilot II in Fig. 1 and control the azimuth or directional base line of the latter by turning ports 22 with respect to the directional gyro cut- ,oil plate 89, thereby serving to automatically steer the craft on a homing course toward any desired station.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In radio compass apparatus for navigable craft, a non-directional antenna, a directional antenna in the form of a center-tapped loop, .mean for positioning said directional antenna application of Alger 8. Riggs, now Patent with respect to the direction of reception of a #2,115,088, dated April 26, 1938.. Generator III is driven by motor 3", having one field III energln'ed from supply leads Ill and its other field I2. connected to transformer H2 in the direction to oppose or buck the audio signal voltage. 5 This opposing voltage of generator I" varies with the speed of motor I". so that as the system approaches a balanced position and the audio signal falls toward zero. such signal is overcome by the speed voltage produced by gena crater Ill, whereby field Ill of motor I" is reversed and the system quickly braked to a stop. By suitable adjustment this system can be made dead-beat and non-hunting.

A switch I2I is included between the output a transformer I22 of push-pull stage III and motor field winding III so as to enable setting the byIeadsIIIacrossLCJuW YIeadsIIOsoas to drive motor I" in a clockwise direction, for

example. When the loop 2 has reached the desired position. the switch III is released and re- I8 and balanced modulator for produc modu-' radio wave from a remote transmitter including.

a reversible motor; a circuit receiving the output of said two antennae, a source or low frequency A. C. connected thereto, electron switching means controlled by saidlow frequency A. C. for alternately connecting the two halves of said loop to said circuit, an amplifier-detector receiving the output of said circuit and biased by said low frequency A. C. for obtaining a signal reversing in phase as said loop passes through its null position and which varies at said low frequency. means for obtaining a reversible polarity D. 0.

signal proportional thereto, means for obtaining D. C. signals proportional to the first and second order time derivatives of said first D. C. signal and means for utilizing said reversible phase low frequency signal and said derivative signals Jointly to control the operation of said revel-able motor.

'2. In a radio compass apparatus for navigable craft, directional and non-directional antennae, a low frequency alternating current supply, rectifiermeansconnectedtosaidmlyandoneof said antennae forservingas-an electronicswitch lated radio frequency signal, amplifying and detecting means for receiving said radio frequency signal and for producing a variable magnitude,

reversible phase audio signal output therefrom amplifyingand phase detector means for recciving said audio signal and for detecting the phase of the directional antenna output, and

compass operating reversible anti-hunting motive meanscontrolled from said amplifying and phase detecting means. i i v 3. In a radio compass apparatus for navigable craft, directional. and non-directional antennae, a low frequency alternating current supply, rectifier means connected to said supply and one ofv said antennae for serving as an electronic switch and balanced modulator for producing a modulated radiofrequency signal, amplifying and detecting means for receiving said radio frequency signal and for producing a variable magntiude, re-

indicator, and further controlling said reversible motive means in accordance with its own velocity to prevent hunting of said indicator about its position of rest.

7. In a radio compass apparatus for navigable craft including a directive and a nonedirective antenna and motive means for orientating. said non-directive antenna, the method of orientatln8 an indicator to indicate the angular relationship of a wave front and said directive antenna which comprises deriving a carrier frequency current from said non-directive antenna, deriving a second carrier frequency current from said directive antenna which varies in amplitude and reverses in phase as a function of said angular relationship, generating currents of modulation frequency, applying said modulation currents to said second carrier current, deriving modulated radio frequency currents from said modulated carrier, combining said first carrier and said modulated radio frequency currents, detecting said combined currents to derive therefrom an audio frequency current, combining said audio frequency current with said modulation current, obtaining the rate of change of the effective value of said combined current and jointly utilizing said com- 4. In a radio compass apparatus for navigable I craft, directional and non-directional antennae, a low frequency alternating current supp rectifier means connected to said supply and said antennae for serving as an electronic switch and balanced modulator for producing a modulated radio'frequency signal, amplifying and detecting means for receiving id radio frequency signal 7 and for producing a v riable magnitude, reversible phase audio signal output therefrom, amplifying and phase detector means for receiving said audio signal and for detecting the phase ofrunning and hunting of said motive means.

5. In radio compass apparatus for navigable craft, directional and non-directional antennae carried by the craftfor receiving signals from a transmitting station, a control circuit fed from said antennae and responsive to the displacement of said directional antennae from null position with respect to said signals and to a time derivative thereof, motive means operated by said control circuit for automatically turning said directional antenna, and a compass indicator operated from said motive means.

' 6. In a radio compass, the method of orientating an indicator which comprises receiving radio frequency signals from a source whose direction is to be indicated, deriving from said signals a car'- rier frequency signal, generating modulation currents, applying said modulation currents to said carrier, amplifying said modulated carrier currents, detecting said amplified modulated carrier to derive a current of modulation frequency which reverses in phase'as, a function of the bearing of. said source, combining said last named reversible phase" current with said modulation current and using said combined currents to control reversible bined current and its rate of change to control said motive means in a dead beat manner and hence the orientation of saiddirective antenna and said indicator as a function of the angular relationship between said directive antenna and said wave front.

8. In a radio compass apparatus, a directional antenna, a reversible motor for orienting said directional antenna, a supply or low frequency alternatlng current, means for -modulating the output of said directional antenna with said low frequency alternating current, a non-directional antenna, amplifier means connected for receiving and amplifying the modulated output of said directional antenna and the output of said non-directional antenna, detector means connected for demodulating the output of said amplifier, a con trol circuit for said reversible motor connected to be supplied from said detector means, said control circuit also being connected to said low frequency alternating current supply, whereby a comparison of the relative phases of the low frequency output of said detector means and said alternating curernt supply is efiected for the purpose of controlling the operation of said motor to maintain said directional antenna in substantially a null position with respect to received electromagnetic waves, and further means for controlling the operation of said motor in accordance with its own speed of rotation to prevent himting.

, 9. In a radio compass apparatus, a directional antenna, a reversible motor for orienting said directional antenna, a supply of low frequency alternating current, means for modulating the output of said directional antenna with said low frequency alternating current, a non-directional antenna, amplifier means connected for receiving and amplifying the modulated output of said directional antenna and the output of said non- I directional antenna, detector means connected for demodulating the output of said amplifier, and a control circuit for said reversible motor connected to be supplied from said detector 7 means, said control circuit also being connected to said low frequency alternating current supply and including means for comparing the phase.

of the low frequency output of said detector motive means efi'ecting the orientation of said means with that of said alternating current our ply, a relative shift of said phases corresponding to movement of said directional antenna from null position with respect to received electromagnetic waves, being utilized by said control circuit to drive said directional antenna back into null position, said control circuit including means for app y to said motor a voltage proportional to the speed at which said directional antenna is driven, said last voltage being applied in a sense to prevent said directional antenna from hunting about its position of rest. 1

10. Radio compass apparatus as claimed in claim 8 in which the means for controlling the motor in accordance with its own speed of rotation includes a generator driven by said motor.

11. Radio compass apparatus as claimed in claim 8 in which the means for controlling the operation of the motor in accordance with its own speedof rotation includes means for utilizing the armature voltage of said motor.

12. Radio compass apparatus for dirigible craft comprising a directional antenna, a non-directional antenna, a source of low frequency A. C.. modulating and combining'means for obtaining from the radio frequency signals received by said two antannae and said low frequency A. C. a reversible phase signal proportional to the angle between said directional antenna and the wave front of a wave radiated by a remote transmitter, power operated means for orienting said directional antenna to a position of minimum reception, a control for said power operated means, manually controlled means for operating said directional antenna to a position of minimum reception, means for indicating the sense and magnitude of the deviation of said directional antenna from said position of minimum reception, means for controllingthe course of the craft in accordance with a reversible electrical signal, switching means for selectively applying said reversible phase antenna-derived signal to the control for said power operated antenna orienting means, to said indicating means, and to said course controlling means.

13. In a radio. compass apparatus for navigable craft, a tumable directional antenna, motive means for orienting said antenna, circuit means fed from said antenna for deriving a control signal indicative of the direction of propagation of received radio waves emanating from a remote transmitter, means for continuously and instantly controlling said motive means in response to said control signal and a time derivative thereof, a compass pointer connected to turn with said antenna,-a fixed scale and a concentric relatively movable compass scale, both saidscales cooperating with said pointer, and means for setting said relatively movable compass scale so that the same may conform with the crafts compass reading, said compass pointer cooperating with said fixed scale to indicate the direction of the transmitter with respect to the craft's headin: and cooperating with said movable scale to indicate the compass bearing of the remote transmitter as well as the reverse bearing thereof.

14. In a radio compass apparatus for navigable craft, a turnable directional antenna, motive means for orientingsaid antenna to the null deriving a control signal indicative of the direcposition with respect to a remote transmitter, a compass pointer connected to'turn with said antenna, circuit means fed from said antenna for tion of propagation of received radio waves emanating from the remote transmitter, means for continuously and instantly controlling said mo-' tive means in response to said control signal and a time derivative thereof, a fixed scale and a concentric relatively movable compass scale, both said scales cooperating with said pointer, means for setting said relatively movable compass scale so that thesame may conform with the crafts compass reading, said compass pointer cooperating with said fixed scale to indicate the direction of the transmitter with respect to the crafts heading and cooperating with said movable scale to indicate the compass bearing of the remote transmitter as, well as the reverse bearing thereof, and a magnetic variation scale arranged concentric with said other scales, whereby the setting of said movable scale with respect to said variation scale may be employed to correct for the magnetic variation at the position of the craft, thereby showing on the movable scale true direct and reverse bearings of said transmitter.

15. In. radio compass apparatus for navigable craft, directional and non-directional antennae carried by the craft for receiving signals from a transmitting station, a control circuit fed from said antennae and responsive to the displacement of said directional antenna from ,null position with respect tothe wave front of said signals, motive means operated by said control circuit, antihunt means connected to said. control circuit and operating in response to the speed of said motive means for providing a corrective signal aiding in the control of said motivemeans for causing the latter to automatically turn said directional antenna in a dead-beat manner.

16. In radio compass apparatus for navigable craft, a non-directional antenna, a directional antenna in the form of a center-tapped loop, means for positioning said directional antenna with respect to the direction of reception of a radio wave from a remote transmitter including, a reversible motor having a motor winding, a circuit receiving the output of said two antennae, a source of low frequency A. C. connected thereto, electron switching means controlled by said low frequency A. C. for alternately connecting the two halves of said loop to said circuit, an amplifierdetector receiving the output of said circuit and biased by said low frequency A. C., for obtaining a signal reversing in phase as said loop passes through its null position and which varies at said low frequency, grid controlled rectifier means electrically coupled to said motor winding, and means employing said reversible. phase and variable signal for controlling said grid controlled rectifier means to produce a graduated control of the output of said gr'id controlled rectifier ,means to efiect continuous and instant response FRANCIS L. MOSELEY. 

